class Counter2 {
    private int count = 0;

    void add() {
        synchronized (this) {
            count++;
        }
    }

    int get() {
        return count;
    }
}

public class Demo21 {
    public static void main(String[] args) throws InterruptedException {
        Counter2 counter2 = new Counter2();

        Thread t1 = new Thread(() -> {
            for (int i = 0; i < 50000; i++) {
                counter2.add();
            }
        });
        Thread t2 = new Thread(() -> {
            for (int i = 0; i < 50000; i++) {
                synchronized (counter2) {
                    counter2.add();
                }
            }
        });
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println("count = " + counter2.get());
    }
}